Sleep not resting on eight-hour pattern

SLAVISH adherents to the eight-hours-a-night sleep rule can relax; new research suggests we all have our own sleep patterns that change according to how much shut-eye we get.

For the first time, a team from the University of Sydney has been able to track people's nightly sleep patterns, finding sleep naturally increases and decreases throughout the week.

''The body seems to have a way of adjusting the amount of sleep we require,'' study leader Chin Moi Chow said. ''If you incur a sleep debt, your body will signal a need to catch up on extra sleep.''

Her study found each person had a different sleep cycle, with some taking only a couple of days to catch up, and some taking up to 18 days. Unlike some previous research, Dr Chow did not find the participants made up for lost sleep at the weekend. Rather, her study's 13 young men, who had their sleep measured over two weeks using a measurement device worn on their arms, made up the sleep at different times, getting up to two hours more sleep on some nights than others.

This suggested the timing of individual cycles was intrinsic rather than something each person chose, she wrote in the journal Nature and Science of Sleep.

The president of the Australasian Sleep Association, Shantha Rajaratnam, said the study suggested the body has an ongoing mechanism for dealing with the amount of sleep we get.

''Over time, it is like you are withdrawing money from the bank, you build up a debt, but eventually, you have to pay back that debt, and after that you can start withdrawing again,'' he said. But he warned it would be dangerous for people to assume they no longer needed eight hours each night.